EP0582913B1 - Switching device - Google Patents

Abstract

The invention relates to a circuit device for charge and discharge monitoring for at least two electrical accumulators (rechargeable batteries) (20) or accumulator cells which are connected in series with one another to a charging current source (28). The device comprises in each case one monitoring module (21) for each accumulator or each accumulator cell, which has a charging current limiting circuit and a first signal transmitter for indicating the operating status of the charging current limiting circuit. The charging current limiting circuit is acted on as a function of a temperature signal which corresponds to the temperature of the accumulator (20) or of the accumulator cell. Connected to the first signal transmitters is a control signal circuit (29) whose output signal is applied to the charging current source (28) in order to control the charging current supplied by it.

Description

The invention relates to a circuit device for charge monitoring for at least two electrical accumulators or accumulator cells connected in series with one another to a charging current source.

Such a device is known from US-A-4,238,721.

If two or more accumulators are connected in series and this series connection is treated as a unit in particular when charging, problems can arise which lead to premature failure of the accumulators. These problems are due to the fact that, due to manufacturing tolerances, each accumulator has its own electrical, chemical and thermal properties.

In particular, due to the scatter of specimens when charging the rechargeable batteries, different end-of-charge currents and different rechargeable battery temperatures caused by the device design can occur, which can lead to different recharging states of the rechargeable batteries and to overcharging of individual rechargeable batteries if the series connection of the rechargeable batteries is treated as a unit of identical rechargeable batteries.

In addition, problems also arise when discharging the accumulators, since individual accumulators or accumulator cells cannot or cannot provide the required capacity. Such accumulators or accumulator cells can be damaged by deep discharge or by reversing the polarity.

These problems lead in particular to closed accumulators, e.g. In the case of so-called drysafe accumulators, failures occur because they cannot be refilled with water.

In order to avoid problems occurring when charging accumulators, various circuit devices, in particular for charging monitoring, have been developed.

In the Thermoguard system from Hagen Batterie AG, the current temperature of the battery is recorded when a single battery is charged and transmitted to a charger. An electrical control circuit is provided in the charger, which adjusts the charging current and thus the charging process of an accumulator as a function of the current accumulator temperature. By means of constant temperature monitoring, the charging process for an accumulator can be optimized so that it can be charged gently in the shortest possible time without fear of damage due to excessive charging current or overcharging.

However, this system is not suitable for a series connection of several accumulators that are to be charged simultaneously.

In another circuit device on the market for monitoring the availability of a stationary accumulator system, the uniform, fully charged state of all accumulators or accumulator cells of the accumulator system is monitored in the charge maintenance mode. In addition, inadmissibly high battery temperatures are determined by monitoring the temperature of a plurality of batteries or battery cells.

During discharge operation, the accumulators or accumulator cells are monitored to determine whether the end of discharge is undershot or whether individual accumulators or accumulator cells are even discharged to such an extent that there is a risk of polarity reversal.

The disturbance events recorded in each case are stored in this known circuit and displayed in a suitable manner. A corresponding acoustic alarm signal is emitted in the event of faults that can directly damage the battery system.

Control of the charger is not provided.

In another control circuit for a charger for accumulators on the market, the accumulator temperature and its terminal voltage are detected by the control circuit arranged on the accumulator, which causes the charger to be operated on and off. From the temperature, a voltage signal corresponding to the optimal terminal voltage at the detected temperature is formed by a temperature-voltage converter and compared with the detected terminal voltage. As long as the terminal voltage is less than the optimal voltage, that of a charger or a suitable generator, e.g. in a motor vehicle, supplied charging current turned on. If the battery terminal voltage reaches the optimal value, the charging current is switched off.

However, this device is not suitable for connecting two or more accumulators in series.

Another circuit device available on the market comprises for each accumulator cell an independent regulator circuit with a shunt line of resistance and Transistor. The transistor is acted upon by a control circuit which detects the respective cell voltage during a charge maintenance operation and, in dependence thereon, adjusts the resistance of the shunt line so that the charge maintenance current required in each case flows through the respective cell.

Although this circuit device protects each battery cell from excessively high trickle charge currents, it is not able to control the charger required for charging or trickle charge operation.

US Pat. No. 4,238,721 also relates to the charging of battery cells connected in series, in which a reduction in the total charging current supplied is already initiated when a single cell is the first to reach a preset reference voltage. As a result, the other cells are subsequently charged with an unnecessarily low charging current, which can lead to incomplete charging of these cells.

The invention has for its object to provide a device for charging monitoring, which ensures the most effective and at the same time individual and gentle full charge individual batteries or accumulator cells in series.

This object is achieved by the features of the characterizing part of claim 1.

According to the invention, therefore, a monitoring module is provided for each individual accumulator or for each individual accumulator cell, by means of which the respective charging current is individually limited to a permissible optimal value. At the same time, a charging current limitation is detected via a control signal circuit which, however, only acts on the charging current source, that is to say a charger or a generator circuit supplying a charging current, in order to reduce the charging current offered, if a charging current limitation has been carried out on all the accumulators or accumulator cells.

According to the invention, the use of the AND circuit for the signals which indicate the operating state of the charging current limiting circuits of the monitoring modules means that the charger or another charging current source provides the full charging current for as long as it is still available from a single accumulator or a single accumulator cell without any risk Damage can be used. As soon as a charging current limitation is required for all accumulators or accumulator cells, the charging current provided by the charging current source is switched down until at least one accumulator or one accumulator cell can fully use the reduced charging current again.

The degree of charge current reduction should be such that the accumulator or the cell in question, which requires the least charge current limitation, receives just enough current that the charge current limitation is then no longer necessary. This minimizes the energy expenditure and at the same time prevents an otherwise possible overload of the charging current limiting circuits.

By using a circuit device according to the invention on a series connection of accumulators or accumulator cells, chargers with a simplified structure can be used.

Due to the gentle and rapid charging of the batteries achieved by means of the circuit device according to the invention, damage to these can be prevented, so that their service life is increased.

The use of the circuit device in electric vehicles, in which current is often fed back into the accumulators when braking, enables the control of the supply generator, so that the accumulators are not overcharged even when the current is fed back into the accumulators in the case of rapid charging.

In order to obtain a temperature-controlled charging current limitation in a particularly expedient manner, the exemplary embodiments according to claims 2 to 4 are provided.

According to claims 5 to 7, the charging current is limited in a simple manner in that too much charging current offered is bypassed to the respective accumulator or the accumulator cell via a shunt line.

In order to avoid overcurrents in the circuit device and thus their impermissible heating, the exemplary embodiments according to claims 8 and 9 are provided.

In a particularly advantageous manner, the circuit device according to the invention can also be used for discharge monitoring if it is designed according to one of claims 10 to 13.

The refinements of the invention according to claims 14 and 15 have the advantage that the circuit device according to the invention provides potential-free signals for controlling the charging current source.

The control signal circuit can be constructed as a logic circuit in accordance with claims 16 to 17.

The second control signals, which indicate an overcurrent in the current limiting circuit during charging and the risk of deep discharge in discharging, are used to control the charging current source or to charge a discharge monitoring circuit with one another via an OR circuit linked so that a signal already present indicates the possible damage to the corresponding monitoring module or an accumulator or an accumulator cell.

Fig. 1

ein schematisches Blockschaltbild einer Schaltungsvorrichtung zur Lade- und Entladeüberwachung von in Reihe geschalteten elektrischen Akkumulatoren,

Fig. 2

ein schematisches Schaltbild der Anschlüsse eines Überwachungsmoduls an einem Akkumulator und

Fig. 3

ein schematisches Schaltbild des Überwachungsmoduls.

The invention is described below, for example with reference to the drawing; in this shows:

Fig. 1

1 shows a schematic block diagram of a circuit device for charging and discharging monitoring of electrical accumulators connected in series,

Fig. 2

a schematic diagram of the connections of a monitoring module on an accumulator and

Fig. 3

a schematic diagram of the monitoring module.

Corresponding components in the various figures of the drawing are identified by the same reference symbols.

As shown in Fig. 1, each of e.g. A monitoring module 21 is assigned to four accumulators 20 connected in series, wherein the monitoring modules 21 are each connected via signal lines 22, 23 to the respective positive and negative connections 24 and 25 of the accumulators 20.

The series connection of the accumulators 20 is connected via lines 26 to a charging output 27 of a charger 28.

The monitoring modules 21 each have first signal outputs 9, 10, at which a potential-free signal can be set and which are connected in series with one another via a first control signal circuit 29 to a first signal input 29 'of the charger 28 are connected. A second signal input 30 'of the charger 28 is connected via a second control signal circuit 30 to second signal outputs 11, 12 of the monitoring modules, to which a second potential-free signal can be set and which are connected in parallel to one another. The second signal outputs 11, 12 are also connected via the second control signal circuit 30 to a signal input 31 of a discharge monitoring circuit 32.

The structure of a monitoring module 21 and its connection to an accumulator 20 is explained in more detail below with reference to FIGS. 2 and 3. To determine the temperature of the associated accumulator 20, each monitoring module 21 has a temperature sensor 33 arranged on the accumulator 20, the connecting terminals 5, 6 of which are connected to the connecting terminals 5 ', 6' of a temperature-voltage converter 34. A temperature-dependent voltage signal is applied by the temperature-voltage converter 34 to the inverting input of a comparator 35. The non-inverting input of the comparator 35 is connected to the center tap of a voltage divider 60 which is connected between the terminal 3 ', which is connected to the terminal 3 at the positive terminal 24 of the accumulator 20, and ground, so that one of the positive accumulator voltage + U _{B the} corresponding voltage is present at the non-inverting input. The signal output of the comparator 35 is applied directly to an input of a first optocoupler 36 serving as a signal transmitter, the phototransistor 37 of which connects the first signal outputs 9, 10 of the monitoring module 21 to one another. Instead of an optocoupler, another galvanically isolating signal transmitter, for example a magnetic coupler with a coil and a magnetic field-dependent resistor, can also be provided as the signal transmitter 36.

The output of the comparator 35 is further connected via a resistor 38 to a control input 39 of a control component with a control circuit, e.g. a power field effect transistor 40 connected.

The line path 41 of the power field effect transistor 40 is connected in series with a resistor 42 between terminals 1 ', 2', one of which has a terminal 1 and the other of which has a terminal 2 at the positive or negative terminal 24 or 25 of the Accumulator 20 is connected.

In this way, a controlled system with a shunt line 41, 42 is created, by means of which the excess current offered by the charger 28 can be conducted past the accumulator 20. For this purpose, the comparator 35 compares a voltage corresponding to the voltage U _B present at the positive terminal 24 of the accumulator 20 with a temperature-dependent voltage signal and supplies an output signal to the control input 39 of the power field-effect transistor 40 if the voltage present at the positive terminal 24 of the accumulator 20 U _B corresponding voltage is greater than the temperature-dependent voltage signal, and thus causes the line path 41 of the field effect transistor 40 to become conductive so that the charging current flows past the accumulator 20 via the shunt line (40, 42). It is important that the charging current is conducted past the accumulator 20 via lines which are not identical to the measuring lines for tapping the accumulator voltage.

For thermal reasons, the power field effect transistor 40 can also be arranged outside the module 21. This avoids possible heating of the remaining electronics by the power field effect transistor.

The output signal of the comparator 35 which is present at the optocoupler 36 has the effect that the collector-emitter path of the phototransistor 37 also becomes conductive. This sets a potential-free signal at the first signal outputs 9, 10.

If this rule occurs in all monitoring modules 21, the excess current offered by charger 28 is conducted past accumulators 20 in all monitoring modules 21, and consequently the potential-free signals are set at all first signal outputs 9, 10 of monitoring modules 21 first control signal circuit 29 a corresponding control signal at the signal input 29 'of the charger 28 and the current supplied by the charger 28 is switched down until one of these first potential-free signals is reset.

A hard-wired AND circuit accordingly has the effect that the charging current offered by the charger 28 is kept at a relatively high level for as long as this current is required for charging at least one accumulator 20.

In order to protect the shunt line via the power field-effect transistor 41 and the resistor 42, and thus the monitoring module 21, from excessively high currents and therefore from excessively high temperatures, a voltage is tapped at the connection point 43 between the field-effect transistor 40 and the current limiting resistor 42 the non-inverting input of a second comparator 44 is applied, at the inverting input of which a reference _voltage U _ref1 is present. The output signal of the second comparator 44 is applied via a diode 45 to an input of a second optocoupler 46 serving as a galvanically isolating signal transmitter, the phototransistor 47 of which with its collector-emitter path is connected between the second signal outputs 11, 12 of the monitoring module. If the voltage tapped at the connection point 43 _exceeds the reference voltage U _ref1 , the collector-emitter path of the phototransistor 47 becomes conductive and the charger 28 detects a corresponding control signal at its second signal input 30 'connected to the second control signal circuit 30 and thus determines that An overcurrent has occurred at least in one monitoring module 21, that is to say a charging current which exceeds the maximum permissible current via the power field-effect transistor.

In this case, the charger 28 immediately switches the charging current offered in stages until the overcurrent is reduced. Through the parallel connection of the individual second signal outputs 11, 12 and thus the phototransistors 47 connecting them through the second control signal circuit 30, a wired OR circuit is obtained. In order to determine at which of the individual accumulators 20 in the monitoring module 21 an overcurrent has occurred, it is possible to switch between the phototransistor 47 and e.g. the second signal output 11, a resistor 48 is connected in series with the collector-emitter path of the phototransistor 47, the individual resistances of the monitoring modules 21 having different resistance values, ie being weighted.

In order to monitor each individual accumulator 20 for a damaging deep discharge during the discharge operation of the accumulators 20, there is between the mass of the monitoring module 21, which is connected to the negative connection 25 of the accumulator via a connection terminal 4 'and an associated connection terminal 4, and with the positive accumulator voltage terminal 3 'switched a voltage divider 49, the center tap 50 is connected to an inverting input of a third comparator 51, to the non-inverting input of a reference voltage U _ref2 is present. The output signal of the third comparator 51 is applied to the optocoupler 46 via a diode 52.

If the voltage on an accumulator drops below a critical value during discharge operation, which may be 10.2 V for 12 V accumulators, for example, but which must be adapted to the particular circumstances, this is detected by the comparator 51 and via that generated by the optocoupler 46 potential-free signal reported to the discharge monitoring circuit 32.

The discharge monitoring circuit 32 either causes a reduction in the maximum permitted discharge current or a disconnection of the load from the batteries when an undervoltage occurs.

An output of a fourth comparator 53 is connected to the control electrode 39 of the field effect transistor 40 via a diode 54 which is connected to the control input 39 by its anode. The inputs of the fourth comparator 53 are connected via connection terminals 7 ', 8' to corresponding connection terminals 7, 8 of a current sensor 55 which detects the charging or discharging current through the respective accumulator 20 in the region of the positive connection 24 of the accumulator 20. In this way, the current direction is thus recognized, so that a discharge of the battery 20 via the shunt line 40, 42 is prevented during charging.

The described device for charging and discharging monitoring can also be used in electric vehicles in which a plurality of accumulators are connected in series to drive an electric motor. In electric vehicles of this type, the electric motor is often operated as a generator when braking, so that current flows into the batteries is fed back. If this current supplied during braking, the recuperation current, is not limited, the batteries can be overcharged, which can cause damage.

In particular, it is also possible to apply the output signal of the third comparator 51 to a third galvanically isolating signal transmitter 56, shown in broken lines in FIG. 3, which then indicates the occurrence of an undervoltage, so that the distinction as to whether an overcurrent during charging or whether there is an undervoltage is present during unloading, is facilitated. This is particularly advantageous if the circuit described is used in an accumulator-driven vehicle, in the driving mode of which the charging or discharging mode alternates as a result of changing acceleration or braking mode.

When using the device described, damage during charging can be prevented by controlling the electric motor operated as a generator or a brake controller assigned to it by the output signals of the monitoring modules, so that the risk of damage to the batteries when braking as a result of overcharging is eliminated.

If damage to the batteries in the event of undervoltage is prevented in the discharge operation by disconnecting the batteries from the load, an "emergency on" circuit must be provided, in particular when using the circuit described in an electric vehicle, so that this does not occur at a danger point stop.

Claims (17)

1. Circuit apparatus for monitoring the charging of at least two electrical accumulators (20) or accumulator cells connected to one another in series with a charging current source (28), the apparatus comprising one monitoring module (21) for each accumulator (20) or for each accumulator cell to be monitored, with each monitoring module (21) having a charging current limitation circuit (40, 42) and a first signal generator (36) for displaying the state of operation of the charging current limitation circuit (40, 42), and further comprising a control signal circuit (29) connected to the first signal generators (36), with the output signal of the control signal circuit being applied to the charging current source (28) in order to control the charging current delivered by it, characterised in that the charging current limitation circuit (40, 42) is acted on in dependence on a temperature signal corresponding to the temperature of the accumulator (20) or of the accumulator cell, and in that the control signal circuit (29) is an AND-circuit.
2. Circuit apparatus in accordance with claim 1, wherein a first comparator circuit (34, 35) is associated with each charging current limitation circuit (40, 42), with the temperature signal and the potential present at an accumulator terminal (24) being supplied to the comparator circuit.
3. Circuit apparatus in accordance with claim 2, wherein the temperature signal is applied to one input of a first comparator (35) via a temperature-voltage converter (34), with the potential present at the accumulator terminal (24) being applied to the other input of the first comparator.
4. Circuit apparatus in accordance with claim 2 or claim 3, wherein the output signal of the comparator circuit (34, 35) is directly applied to the first signal generator (36) and is applied to the charging current limitation circuit (40, 42) via a resistor (38).
5. Circuit apparatus in accordance with any one of the preceding claims, wherein a bypass line (40, 42) with a variable resistance (41) is connected in parallel to the accumulator (20) or to the accumulator cell as the charging current limitation circuit.
6. Circuit apparatus in accordance with claim 5, wherein the bypass line (40, 42) has a resistor (42) and connected in series therewith a regulating component (40) with a control circuit, the control input (39) of which is acted on in dependence on the temperature signal.
7. Circuit apparatus in accordance with claim 6, wherein a power transistor with a control circuit, in particular a field-effect power transistor (40), is provided as the regulating component.
8. Circuit apparatus in accordance with claim 5, claim 6 or claim 7, wherein each monitoring module (21) has an overcurrent protection circuit (43, 44, 45) connected to a second signal generator (46), with the outputs (11, 12) of the second signal generators (46) being connected to a second control signal circuit (30), the output signal of which is applied to the charging current source (28).
9. Circuit apparatus in accordance with claim 8, wherein the overcurrent protection circuit includes a comparator (44) to the one input of which there is applied a voltage signal corresponding to the current in the bypass line (40, 42) and to the other input of which there is applied a reference signal.
10. Circuit apparatus for the charge and discharge monitoring of at least two electrical accumulators (20) or accumulator cells connected to one another in series with a charging current source in accordance with claim 1, wherein each monitoring module (21) has a third comparator circuit (49, 51, 52) to which the voltage present at the accumulator terminal (24) is applied and the output signal of which acts on a signal generator (46).
11. Circuit apparatus in accordance with claim 10, wherein the comparator circuit has a potential divider (49) lying between the positive and the negative terminals (24 and 25 respectively) of the accumulator (20) or of the accumulator cell, with the central tap (50) of the potential divider being connected to one input of a comparator (51), and with a reference signal being applied to the other input of the comparator (51).
12. Circuit apparatus in accordance with claim 10 or claim 11, wherein the output signal of the signal generator (46, 56) acted on by the third comparator circuit is applied via a corresponding control signal circuit (31) to a discharge monitoring circuit (32).
13. Circuit apparatus in accordance with one of the preceding claims, wherein the signal generators (36, 46, 56) are formed as galvanically separating signal generators.
14. Circuit apparatus in accordance with claim 13, wherein the signal generators are formed as optic couplers (36, 46) having phototransistors (37, 47), and wherein the collector-emitter paths of the phototransistors (37, 47) are connected with the respective control signal circuit (29, 30).
15. Circuit apparatus in accordance with claim 14, wherein in each case a weighted resistor (48) is connected in series with the collector-emitter path of the respective phototransistor (47) of the second signal generator (46).
16. Circuit apparatus in accordance with one of the preceding claims, wherein the respective control signal circuit (29, 30) is a logic circuit, preferably a hard-wired logic circuit.
17. Circuit apparatus in accordance with claim 4 to claim 16, wherein the second control circuit (30) is an OR-circuit.

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